Apparatus and methods for depositing molten metal onto a foil substrate

ABSTRACT

A web coating platform for depositing molten metal on flexible substrates is provided. The web coating platform can be used for manufacturing solid lithium anodes for use in energy storage devices, for example, rechargeable batteries. The coating platform can be designed for double-sided coating of a continuous flexible substrate (e.g., a copper foil) with molten lithium followed by double-sided lamination or passivation. The coating platform integrates novel coating elements unique to handling and processing molten metals. For example, some implementations of the present disclosure incorporate double-sided molten metal coating elements, which include at least one of a molten metal application assembly (e.g., kiss roller, slot-die, Meyer bar, and/or gravure roller), a primary melt pool assembly, a secondary melt pool assembly, and an engagement mechanism.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.16/996,506, filed Aug. 18, 2020, which claims benefit of U.S. Prov.Appl. No. 62/894,144, filed Aug. 30, 2019, which are herein incorporatedby reference in their entirety.

BACKGROUND Field

Implementations described herein generally relate to continuous webprocessing systems and more specifically to systems and methods fordeposition of molten metals on continuous web substrates.

Description of the Related Art

Flexible substrates are utilized in many applications in the manufactureof energy storage devices. One such application is the deposition ofmaterials onto a flexible substrate in the manufacture of high-capacityenergy storage devices, such as lithium-ion (Li-ion) batteries.

The current generation of energy storage devices (e.g., Li-ionbatteries) use graphite based negative electrode deposited on thincopper substrates (e.g., ˜8 μm). A new negative electrode with highenergy density is needed to improve energy density of the energy storagedevice. Alkali metal anodes (e.g., lithium metal anodes) are believed toprovide the targeted high energy density. However, current alkali metaldeposition processes including extrusion and evaporation suffer fromseveral deficiencies. For example, extruding alkali metal to high-puritysingle digit micron thickness suitable for negative electrodes isdifficult if not impossible. Lithium deposition by evaporation usingpowder lithium sources present several safety related issues. Thus,there is no practical solution for high throughput high purity alkalimetal deposition for lithiation and alkali metal anodes.

One method for manufacturing anode electrodes and cathode electrodes forenergy storage devices is principally based on depositing thin films ofcathodically active or anodically active material onto a flexiblesubstrate serving as a conductive current collector. Conventionally, theflexible substrate is referred to as a web that is wound through aseries of rotatable rollers in a deposition apparatus. Deposition ontothe web is performed on or between the rollers. Drying of the depositedmaterial can be performed on or between the rollers after thedeposition.

However, deposition of molten metals on continuous web substratespresents several challenges. For example, contact between the moltenmetal and continuous web material often leads to expansion of thecontinuous web material. Due to this expansion of the continuous webmaterial, conventional deposition systems have issues with controllingthe flatness and/or deflection of the web during deposition. Forexample, deflection in an axial direction and/or a cross-web directioncauses non-uniform deposition resulting in non-uniform thicknesses inthe deposited material.

Accordingly, there is a need in the art for methods, systems andapparatus for deposition of molten metals on continuous web substrates.

SUMMARY

Implementations described herein generally relate to continuous webprocessing systems and more specifically to systems and methods fordeposition of molten metals on continuous web substrates. In one aspect,a system is provided. The system includes a chamber body defining aninterior volume, a first partition plate extending across the interiorvolume separating the interior volume into a processing volume and anunwinding volume, a second partition plate extending across the interiorvolume separating the interior volume into the processing volume and awinding volume, a reel-to-reel system operable to transport a continuousflexible substrate, and a molten metal coating assembly positioned inthe processing volume. The reel-to-reel system includes an unwindingroller positioned in the unwinding volume, on which the continuousflexible substrate is wound prior to processing, and operable to unwindand release the continuous flexible substrate for processing. Thereel-to-reel system further includes a winding roller positioned in thewinding volume and operable to receive the continuous flexible substratefollowing processing, and operable to wind the continuous flexiblesubstrate thereon. The molten metal coating assembly includes a kissroller having a surface that picks up by contact a wet film comprisingmolten metal and deposits the wet film on the continuous flexiblesubstrate, a primary melt pool operable to supply the molten metal tothe kiss roller, a secondary melt pool operable to replenish the moltenmetal in the primary melt pool, and an engagement mechanism coupled withthe secondary melt pool and operable to move the secondary melt poolradially toward and radially away from the primary melt pool.

Implementations can include one or more of the following. The systemfurther includes a Meyer rod positioned downstream from the kiss rollerand upstream from the winding roller, and operable to control a shape ofthe molten metal deposited on the continuous flexible substrate by thekiss roller. The system further includes a laminate film supply rollerpositioned in the winding volume and operable to supply a laminate filmover the deposited molten metal. The system further includes one or moreauxiliary tension reels disposed along a travel path where thecontinuous flexible substrate is conveyed between the unwinding roller,the kiss roller, and the winding roller. The engagement mechanism is apneumatic cylinder. The kiss roller includes one or more internalheaters. The surface of the kiss roller is a convex surface. The primarymelt pool is positioned on a heater operable to maintain the moltenmetal in a molten state.

In another aspect, a system is provided The system includes a chamberbody defining an interior volume, a first partition plate extendingacross the interior volume separating the interior volume into aprocessing volume and an unwinding volume, a second partition plateextending across the interior volume separating the interior volume intothe processing volume and a winding volume, a reel-to-reel systemoperable to transport a continuous flexible substrate, and a moltenmetal coating assembly positioned in the processing volume. Thereel-to-reel system includes an unwinding roller positioned in theunwinding volume, on which the continuous flexible substrate is woundprior to processing, and operable to unwind and release the continuousflexible substrate for processing. The reel-to-reel system furtherincludes a winding roller positioned in the winding volume and operableto receive the continuous flexible substrate following processing, andoperable to wind the continuous flexible substrate thereon. The moltenmetal coating assembly includes a first slot-die operable to deposit awet film comprising molten metal on a first surface of the continuousflexible substrate, a primary melt pool operable to supply the moltenmetal to the first slot-die, a secondary melt pool operable to replenishthe molten metal in the primary melt pool, and an engagement mechanismcoupled with the secondary melt pool and operable to move the secondarymelt pool radially toward and radially away from the primary melt pool.

Implementations can include one or more of the following. The systemfurther includes a second slot-die operable to deposit the wet filmcomprising molten metal on a second surface of the continuous flexiblesubstrate. The first slot-die includes one or more internal heatersoperable to control a temperature of the molten metal within the firstslot-die. The system further includes one or more process rollersdisposed along a travel path over which the continuous flexiblesubstrate is conveyed between the unwinding roller, the first slot-die,and the winding roller. The process rollers are positioned so that thefirst slot-die deposits molten metal on the continuous flexiblesubstrate while the continuous flexible substrate travels over one ofthe process rollers. The process rollers further include an internalheater. The system further includes a laminate film supply rollerpositioned in the winding volume and operable to supply a laminate filmover the deposited molten metal. The system further includes one or moreauxiliary tension reels disposed along a travel path where thecontinuous flexible substrate is conveyed between the unwinding roller,the first slot-die, and the winding roller. The engagement mechanism isa pneumatic cylinder. The primary melt pool is positioned on a heateroperable to maintain the molten metal in a molten state.

In yet another aspect, a system is provided. The system includes achamber body defining an interior volume, a first partition plateextending across the interior volume separating the interior volume intoa processing volume and an unwinding volume, a second partition plateextending across the interior volume separating the interior volume intothe processing volume and a winding volume, a reel-to-reel systemoperable to transport a continuous flexible substrate, and a moltenmetal coating assembly positioned in the processing volume. Thereel-to-reel system includes an unwinding roller positioned in theunwinding volume, on which the continuous flexible substrate is woundprior to processing, and operable to unwind and release the continuousflexible substrate for processing. The reel-to-reel system furtherincludes a winding roller positioned in the winding volume and operableto receive the continuous flexible substrate following processing, andoperable to wind the continuous flexible substrate thereon. The moltenmetal coating assembly further includes a gravure roller having apatterned surface that picks up by contact a wet film comprising moltenmetal and deposits the wet film on the continuous flexible substrate, aprimary melt pool operable to supply the molten metal to the gravureroller, a secondary melt pool operable to replenish the molten metal inthe primary melt pool, and an engagement mechanism coupled with thesecondary melt pool and operable to move the secondary melt poolradially toward and radially away from the primary melt pool.

Implementations can include one or more of the following. The systemfurther includes a doctor blade positioned to removes excess moltenmetal from the gravure roller so that only patterned portions of thepatterned surface of the gravure roller hold molten metal. The systemfurther includes a laminate film supply roller positioned in the windingvolume and operable to supply a laminate film over the deposited moltenmetal. The system further includes one or more auxiliary tension reelsdisposed along a travel path where the continuous flexible substrate isconveyed between the unwinding roller, the gravure roller, and thewinding roller. The engagement mechanism is a pneumatic cylinder. Thegravure roller includes one or more internal heaters. The primary meltpool is positioned on a heater operable to maintain the molten metal ina molten state.

In yet another aspect, a non-transitory computer readable medium hasstored thereon instructions, which, when executed by a processor, causesthe process to perform operations of the above apparatus and/or method.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe implementations, briefly summarized above, may be had by referenceto implementations, some of which are illustrated in the appendeddrawings. It is to be noted, however, that the appended drawingsillustrate only typical implementations of this disclosure and aretherefore not to be considered limiting of its scope, for the disclosuremay admit to other equally effective implementations.

FIG. 1A illustrates a cross-sectional view of one implementation of anenergy storage device including a lithium electrode structure formedaccording to one or more implementations described herein;

FIG. 1B illustrates a cross-sectional view of a dual-sided electrodestructure incorporating a lithium electrode structure formed accordingto one or more implementations described herein;

FIG. 2 illustrates a schematic cross-sectional view of a roll-to-rollcoating system according to one or more implementations describedherein;

FIG. 3A illustrates a schematic cross-sectional view of one example of akiss coating module according to one or more implementations describedherein;

FIG. 3B illustrates a schematic cross-sectional view of one example of akiss roller that can be used with the coating module of FIG. 3Aaccording to one or more implementations of the present disclosure;

FIG. 4 illustrates a schematic cross-sectional view of one example of aslot-die coating module according to one or more implementationsdescribed herein;

FIG. 5 illustrates a schematic cross-sectional view of one example of agravure coating module according to one or more implementationsdescribed herein; and

FIG. 6 illustrates a process flow chart summarizing one implementationof a processing sequence of forming a passivated lithium electrodestructure according to one or more implementations of the presentdisclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneimplementation can be beneficially incorporated in other implementationswithout further recitation.

DETAILED DESCRIPTION

The following disclosure describes energy storage devices, for example,anode electrodes, high performance electrochemical cells, capacitors andbatteries including the aforementioned electrodes, and apparatus andmethods for fabricating the same. Certain details are set forth in thefollowing description and in FIGS. 1A-6 to provide a thoroughunderstanding of various implementations of the disclosure. Otherdetails describing well-known structures and systems often associatedwith molten metal deposition and energy storage devices are not setforth in the following disclosure to avoid unnecessarily obscuring thedescription of the various implementations.

Many of the details, dimensions, angles and other features shown in theFigures are merely illustrative of particular implementations.Accordingly, other implementations can have other details, components,dimensions, angles and features without departing from the spirit orscope of the present disclosure. In addition, further implementations ofthe disclosure can be practiced without several of the details describedbelow.

Generally, for molten metal deposition, the molten metal remains in amolten state prior to deposition onto the substrate. However, prematuresolidification can change the state of the molten material such that amaterial transfer onto the substrate is no longer possible by wetting,spreading and solidification. A slight drop in temperature can alter theviscosity of the material to the point that the material transfer andthe flow behavior of the molten material leads to inconsistentdeposition thicknesses and non-uniformities. Adhesion and “stickiness”of some materials, for example, lithium, change dramatically withtemperature. A slight drop in temperature can lead to a stickiness, orviscosity change and partial solidification that can tear the substratematerial. For these reasons, in some implementations, the surfacetemperature of the deposition applicators should remain above the melttemperature of the metal. There are multiple methods of heating andcontrolling a surface temperature of such applicators. The heatingmethod can change with the size and operational parameters of theapplicator, being a rotating roller (e.g., kiss roller, Meyer bar, orgravure roller) or a stationary bar (e.g., comma bar, doctor blade).

Implementations described herein will be described below in reference toa roll-to-roll coating system. The apparatus description describedherein is illustrative and should not be construed or interpreted aslimiting the scope of the implementations described herein. It shouldalso be understood that although described as a roll-to-roll process,the implementations described herein can be performed on discretesubstrates.

Implementations described herein refer to a roll-to-roll coating systemadapted for deposition of molten metal on a flexible substrate such as aweb used for example, for lithium-ion battery devices. In particular,the roll-to-roll coating system is adapted for continuous processing ofa flexible substrate such as a web unwound from an unwinding module. Insome implementations, the roll-to-roll coating system is configured in amodular design, for example, an appropriate number of process modulescan be arranged adjacent to each other in a processing line, and theflexible substrate is inserted into the first process module and can beejected from the last process module of the line. Furthermore, theentire roll-to-roll coating system can be reconfigured if a change ofindividual processing operations is targeted.

According to some implementations described herein, the directdeposition of low melting metal or alloys can be done either in vacuumconditions or suitable atmospheric ambient. Some typical examples of lowmelting temperature elements (e.g., below 700 degree Celsius; below 800degree Celsius; or below 1,000 degree Celsius) that can be depositedusing the implementations described herein are alkali metal (e.g.,lithium and sodium), magnesium, zinc, cadmium, aluminum, gallium,indium, thallium, tin, lead, antimony, bismuth, and tellurium. In oneimplementation, the low melting temperature metal is selected from thegroup consisting of alkali metals, magnesium, zinc, cadmium, aluminum,gallium, indium, thallium, tin, lead, antimony, bismuth, and tellurium,alkali earth metals, silver, and combinations thereof. In someimplementations, the molten metal is formed from metals having a meltingtemperature less than 1,000 degrees Celsius. In some implementations,the molten metal is formed from an alkali metal source. In someimplementations, the molten metal is formed from a lithium metal source.In some implementations, the molten metal is molten lithium.

The term substrate as used herein can be considered to include amongother things, webs, flexible materials, porous polymeric materials,films, current collectors, conductive films (e.g., copper or aluminum),foils, webs, strips of plastic material, metal, paper, or othermaterials. The term substrate shall also embrace other types of flexiblesubstrates. A flexible substrate can be moved while being processed in avacuum chamber. For example, the flexible substrate is transported alonga substrate transportation path past coating devices while being coated.In some implementations, the substrate can be unwound from a first roll,transported over the outer surface of a processing drum, e.g. a coatingdrum, and guided along the outer surfaces of additional rollers ordrums. The coated flexible substrate is then wound onto a second roll.Typically, the terms “web,” “foil,” “strip,” “substrate” and the likeare used synonymously.

Substrates, e.g. webs and foils, for use in implementations describedherein can be planar substrates with flat main surfaces or can benon-planar substrates with uneven surfaces. Substrates can also haveboth planar and non-planar surfaces.

In one or more implementations, the substrate can include, but is notlimited to, a plastic sheet or web, a plastic film, paper sheet, fiberstructure, or web, or any other type of substrate. In one or moreimplementations, the term substrate includes multi-layer structures. Forexample, a polymer film coated with one or more metallic layers, such asa copper film, and deposited on a polymer substrate.

It is noted that while the particular substrate on which someimplementations described herein can be practiced is not limited, it isparticularly beneficial to practice the implementations on flexiblesubstrates, including for example, web-based substrates, panels anddiscrete sheets. The substrate can also be in the form of a foil, afilm, or a thin plate.

It is also noted here that a flexible substrate or web as used withinthe implementations described herein can typically be characterized inthat it is bendable. The term “web” can be synonymously used to the term“strip” or the term “flexible substrate.” For example, the web asdescribed in implementations herein can be a foil.

It is further noted that in some implementations where the substrate isa vertically oriented substrate, the vertically oriented substrate canbe angled relative to a vertical plane. For example, in someimplementations, the substrate can be angled from between about 1 degreeto about 20 degrees from the vertical plane. In some implementationswhere the substrate is a horizontally oriented substrate, thehorizontally oriented substrate can be angled relative to a horizontalplane. For example, in some implementations, the substrate can be angledfrom between about 1 degree to about 20 degrees from the horizontalplane. As used herein, the term “vertical” is defined as a major surfaceor deposition surface of the flexible conductive substrate beingperpendicular relative to the horizon. As used herein, the term“horizontal” is defined as a major surface or deposition surface of theflexible conductive substrate being parallel relative to the horizon.

Solid lithium metal anodes for rechargeable battery manufacture aretypically composed of a six to ten micron thick or thicker copper foilcoated on both sides with lithium metal. The lithium metal thicknesstypically depends on the deposition method and parameter chosen. Forexample, for kiss roller coating, the ranges from one to ten microns andis generally equal thickness on both sides. In some implementations, thelithium metal thickness ranges from eight to twenty microns.

Numerous methods exist for producing double-sided lithium metal anodes.Methods are either a single deposition pass process on each face in aserial process or a simultaneous double-sided deposition pass process.Deposition modes differ in the temperature and physical state (e.g.,solid, liquid, or vapor) of the lithium used to coat the copper foil.

In some implementations, a web coating platform for depositing moltenmetal on flexible substrates is provided. The web coating platform canbe used for manufacturing solid lithium anodes for use in energy storagedevices, for example, rechargeable batteries. The coating platform canbe designed for double-sided coating of a continuous flexible substrate(e.g., a copper foil) with molten lithium followed by double-sidedlamination or passivation. The double-sided coating can be achieved bysimultaneous deposition on opposing sides of the continuous flexiblesubstrate. The double-sided coating can be achieved by sequentialdeposition on opposing sides of the continuous flexible substrate. Thecoating platform integrates novel coating elements unique to handlingand processing molten metals. For example, some implementations of thepresent disclosure incorporate double-sided molten metal coatingelements, which include at least one of a molten metal applicationassembly (e.g., kiss roller, slot-die, Meyer bar, and/or gravureroller), a primary melt pool assembly, a secondary melt pool assembly,and an engagement mechanism.

In some implementations, the molten metal application assembly isheated. The molten metal application assembly can be heated by, forexample, a coaxial cartridge heater, which keeps the wetted surfacesabove the metal media melting temperature to prevent prematuresolidification of the molten metal. The molten metal applicationassembly also functions as a metering device controlling the gap andshape of the downstream molten metal meniscus. Controlling the gap andshape of the downstream molten metal meniscus helps control the coatingthickness.

In some implementations, where the molten metal application assemblyincludes rollers, the rollers include sliding portions. The slidingportions are axially separated from the wetted portions and sized toprovide minimal friction against the substrate. The molten metalapplication assembly is supported by slide assemblies at each end andthus operable to travel radially relative to the substrate. In someimplementations, to ensure continuous contact of the sliding portionswith the web the movable part of the slides is spring loaded. Constantforce hydraulic cylinders, constant force pneumatic cylinders, andmotorized sliders are alternatives. Preloading the molten metalapplication assembly against the web compensates for the thermalexpansion of the gap defining components during thermal ramping andchanges.

In some implementations, the primary melt pool supplies molten metal tothe molten metal application assembly enabling the transfer of moltenmetal onto the continuous flexible substrate. The secondary metal poolreplenishes the supply of molten metal in the primary melt pool. Theprimary melt pool and the secondary melt pool are each independentlyheated. Each melt pool can be heated by one or more cartridge heaters,which keep the molten metal in the molten state. In addition, the moltenmetal coating process is typically sensitive to temperaturefluctuations, which change the rheological parameters of the moltenmetal. The secondary melt pool replenishes the primary melt pool withmolten metal at a controlled temperature. Since the two pools aredecoupled from each other, the secondary melt pool can be used to meltmetal ingots.

As the molten metal is transferred from the primary melt pool to thesubstrate via the molten metal application assembly, the liquid level inthe primary melt pool is depleted over time. Pool level changes can haveadverse consequences on the film thickness uniformity. Several methodscan be applied to replenish the primary melt pool. Matching thedepletion rate precisely with the replenishing rate is not trivial sinceprocess changes affect the depletion rate directly. In general, the flowrates are relatively low in the case of thin films, for example, in therange of one to tens of microns. In one implementations, the primarymelt pool is overflowed by oversupplying fresh melt. The secondary meltpool can be used for pre-melting the metal and periodically pouring themolten metal into the primary melt pool. In one example, the secondarymelt pool is a hinged pool and an actuator controls the tilt of thesecondary melt pool causing the molten metal to flow over a ledge intothe primary melt pool. A load cell signal can provide a direct weightmeasurement of the primary pool, which is fed back to a controller. Oneor more sensors (optical, capacitive, ultrasonic or the like) can beused to detect the lower and upper level range respectively and providethe signals to the controller for the actuator motion. The actuator canbe a pneumatic cylinder plumbed to a proportional control valve.

In some implementations where the molten metal is molten lithium,another feature can be added to the secondary melt pool. Lithiumtypically has contaminants, for example, Li₂O₃, LiN₃, that have atendency to float on top of the melt due to the very high surfacetension. Relatively heavy contaminants sink to the bottom of the melt.These heavy contaminants are not desirable in the final deposited filmand thus should remain outside of the primary melt pool. Thereplenishment melt comes from somewhere between the bottom and the topof the secondary melt pool. A spout is positioned in the secondary meltpool that enables molten metal being drawn form a zone with minimalcontaminant concentration.

Since the molten metal application assembly and melt pools aremaintained at a temperature above the melt temperature of the metal,handling and routing of the continuous flexible substrate can becomedifficult due to thermal expansion if the path cannot be expanded. Inone implementation, the engagement mechanism provides separation of themolten metal application assembly from the supported continuous flexiblesubstrate. This separation allows for thermal expansion of thecontinuous flexible substrate without damaging the continuous flexiblesubstrate.

In operation, the molten metal application assembly and melt pools areheated. In one example, the secondary melt pool is used to melt themetal ingots and maintain ample supply to compensate for refilling thedepleted molten metal from the primary melt pool. The primary melt poolis either used to melt the initial ingots or filled from the secondarymelt pool. Once there is enough molten metal available in the primarymelt pool, the comma bar assembly is exposed to a wetting process. Insome implementations, the molten metal application assembly is heatedduring the wetting process. Next, the continuous flexible substrate isadvanced and the molten metal application assembly is engaged with thecontinuous flexible substrate. The molten metal is then transferred ontoand coats the continuous flexible substrate in a defined manner (widthand thickness). This process is sustained until a targeted length of theflexible substrate is coated. At the end of the coating process, themolten metal application assembly is disengaged from the continuousflexible substrate to avoid overexposure. The metal can be solidifiedand melted again for the next run.

In some implementations where the molten metal is highly reactive (e.g.,molten lithium), the comma bar coating process is performed inside anargon environment due to the reactivity of the molten metal material.Both the process and continuous flexible substrate handling assembly arepositioned inside a sealed processing environment filled with argonhaving controlled moisture and oxygen levels. An automated controlmechanism can be used to control the level of molten metal in theprimary and/or secondary melt pools with the help of a pump or apressurized source tank, a level sensor, a shut-off valve and controllogic. Argon gas can be recycled using for example, an air compressor.

FIG. 1A illustrates a cross-sectional view of one implementation of anenergy storage device 100 including a lithium electrode structure formedaccording to implementations described herein. The energy storage device100 can be a lithium-ion energy storage device that uses solidelectrolytes (e.g., a solid-state battery) as well as a lithium-ionenergy storage device, which uses a liquid or polymer electrolyte. Insome implementations, the energy storage device 100 is a capacitor(e.g., supercapacitor or ultra-capacitor). In some implementations, theenergy storage device 100 is combined with other cells to form arechargeable battery or capacitor. The energy storage device 100 has apositive current collector 110, a positive electrode structure 120, aseparator 130, a negative electrode structure 140, and a negativecurrent collector 150. The negative electrode structure is a lithiumelectrode structure formed according to implementations describedherein. Note in FIG. 1A that the current collectors are shown to extendbeyond the stack, although it is not necessary for the currentcollectors to extend beyond the stack, the portions extending beyond thestack can be used as tabs.

The current collectors 110, 150, on positive electrode structure 120 andnegative electrode structure 140, respectively, can be identical ordifferent electronic conductors. Examples of metals that the currentcollectors 110, 150 can be comprised of include aluminum (Al), copper(Cu), zinc (Zn), nickel (Ni), cobalt (Co), tin (Sn), silicon (Si),manganese (Mn), magnesium (Mg), alloys thereof, and combinationsthereof. The current collectors 110, 150 can include metal (e.g.,copper) deposited on a substrate, such as, a polymer substrate.

In some implementations, the negative electrode structure 140 is alithium metal film or a lithium metal alloy film formed according toimplementations described herein. In some implementations, where thenegative electrode structure 140 includes lithium metal, the lithiummetal can be deposited using the molten metal application assembly andthe methods described herein. The negative electrode structure 140 canbe constructed from lithium metal, a lithium alloy foil (e.g. lithiumaluminum alloys), or a mixture of a lithium metal and/or lithium alloyand materials such as carbon (e.g. coke, graphite), nickel, copper, tin,indium, silicon, oxides thereof, or combinations thereof. In someimplementations, the negative electrode structure 140 has a thicknessfrom about 0.5 μm to about 20 μm (e.g., from about 1 μm to about 10 μm;from about 5 μm to about 10 μm).

In some implementations, the negative electrode 140 is constructed froma graphite, silicon-containing graphite (e.g., silicon (<5%) blendedgraphite), a lithium metal foil or a lithium alloy foil (e.g. lithiumaluminum alloys), or a mixture of a lithium metal and/or lithium alloyand materials such as carbon (e.g. coke, graphite), nickel, copper, tin,indium, silicon, oxides thereof, or combinations thereof. The negativeelectrode 140 includes intercalation compounds containing lithium orinsertion compounds containing lithium.

In some implementations, where the negative electrode 140 is constructedfrom graphite or silicon-containing graphite, a pre-lithiation layer(e.g., lithium metal film) is formed on the negative electrode 140 usingthe systems and processes described herein. The lithium metal filmreplenishes lithium lost from first cycle capacity loss of the negativeelectrode 140. The lithium metal film can be a thin lithium metal film(e.g., 20 microns or less; from about 1 micron to about 20 microns; orfrom about 2 microns to about 10 microns).

The positive electrode structure 120 or cathode can be any materialcompatible with the anode and can include an intercalation compound, aninsertion compound, or an electrochemically active polymer. Suitableintercalation materials include, for example, lithium-containing metaloxides, MoS₂, FeS₂, MnO₂, TiS₂, NbSe₃, LiCoO₂, LiNiO₂, LiMnO₂, LiMn₂O₄,V₆O₁₃ and V₂O₅. Suitable lithium-containing oxides can be layered, suchas lithium cobalt oxide (LiCoO₂), or mixed metal oxides, such asLiNi_(x)Co_(1-2x)MnO₂, LiNiMnCoO₂ (“NMC”), LiNi_(0.5)Mn_(1.5)O₄,Li(Ni_(0.8)Co_(0.15)Al_(0.05))O₂, LiMn₂O₄, and doped lithium richlayered-layered materials, wherein x is zero or a non-zero number.Suitable phosphates can be iron olivine (LiFePO₄) and it is variants(such as LiFe_((1-x))Mg_(x)PO₄), LiMoPO₄, LiCoPO₄, LiNiPO₄, Li₃V₂(PO₄)₃,LiVOPO₄, LiMP₂O₇, or LiFe_(1.5)P₂O₇, wherein x is zero or a non-zeronumber. Exemplary fluorophosphates can be LiVPO₄F, LiAlPO₄F,Li₅V(PO₄)₂F₂, Li₅Cr(PO₄)₂F₂, Li₂CoPO₄F, or Li₂NiPO₄F. Exemplarysilicates can be Li₂FeSiO₄, Li₂MnSiO₄, or Li₂VOSiO₄. An exemplarynon-lithium compound is Na₅V₂(PO₄)₂F₃.

In some implementations of a lithium-ion cell according to the presentdisclosure, the negative electrode structure 140 is a lithium metal filmformed according to methods described herein and the positive electrodestructure 120 is lithium manganese oxide (LiMnO₄) or lithium cobaltoxide (LiCoO₂). The energy storage device 100, even though shown as aplanar structure, can also be formed into a cylinder by reeling thestack of layers; furthermore, other cell configurations (e.g., prismaticcells, button cells) can be formed.

In one implementation, the separator 130 is a porous polymericion-conducting polymeric substrate. In one implementation, the porouspolymeric substrate is a multi-layer polymeric substrate. In someimplementations, the separator 130 includes any commercially availablepolymeric microporous membranes (e.g., single or multi-ply), forexample, those products produced by Polypore (Celgard® LLC., ofCharlotte, N.C.), Toray Tonen (Battery separator film (BSF)), SK Energy(lithium ion battery separator (LiBS), Evonik industries (SEPARION®ceramic separator membrane), Asahi Kasei (Hipore™ polyolefin flat filmmembrane), and DuPont (Energain®). In some implementations, where theenergy storage device 100 is a solid-state storage device, the separator130 is replaced with a solid-state electrolyte layer.

In some implementations, the electrolyte infused in cell components 120,130, and 140 is comprised of a liquid/gel or a solid polymer and can bedifferent in each. In some implementations, the electrolyte primarilyincludes a salt and a medium (e.g., in a liquid electrolyte, the mediumcan be referred to as a solvent; in a gel electrolyte, the medium can bea polymer matrix). The salt can be a lithium salt. The lithium salt caninclude, for example, LiPF₆, LiAsF₆, LiCF₃SO₃, LiN(CF₃SO₃)₃, LiBF₆, andLiClO₄, BETTE electrolyte (commercially available from 3M Corp. ofMinneapolis, Minn.) and combinations thereof.

FIG. 1B illustrates a cross-sectional view of a dual-sided electrodestructure 170 that is formed according to implementations describedherein. The dual-sided electrode structure 170 can be combined with acathode electrode structure to form an energy storage device. Althoughthe dual-sided electrode structure 170 is depicted as a dual-sidedelectrode structure, it should be understood that the implementationsdescribed herein also apply to single-sided electrode structures. Thedual-sided electrode structure 170 includes the negative currentcollector 150 with a negative electrode structure 140 a, 140 b(collectively 140) formed on opposing sides of the negative currentcollector 150.

In some implementations, the negative electrode structures 140 a, 140 beach have a protective film 160 a, 160 b (collectively 160) formedrespectively thereon for protecting the negative electrode structure 140from contaminants, such as ambient oxidants. In implementations wherethe negative electrode 140 has a pre-lithiation layer (e.g., lithiummetal layer) formed thereon, the protective film 160 is formed on thepre-lithiation layer. The protective film 160 can be a laminate filmand/or a passivation film. The protective film 160 can be permeable toat least one of lithium ions and lithium atoms. The protective film 160provides surface protection of the negative electrode structure 140,which allows for handling of the negative electrode structure 140 in adry room and can contribute to stable SEI formation. Examples ofmaterials that can be used to form the protective film 160 include, butare not limited to, a lithium fluoride (LiF) film, a lithium carbonate(Li₂CO₃) film, a lithium oxide film, a lithium nitride (Li₃N) film, alithium phosphate (Li₃PO₄) film, a lithium chloride (LiCl) film, lithiumalkyl silanolate based film, an alkyl siloxane based film, apolyethylene (PE) film, a polypropylene (PP) film, a polystyrene (PS)film, or other polymer film that does not react with lithium, apoly(acrylic acid), ethylene vinyl acetate, or other polymer film thatreacts with lithium, or combinations thereof.

The protective film 160 can be formed on the negative electrodestructure 140 or pre-lithiation layer by vapor deposition methods, forexample, chemical vapor deposition (CVD), atomic layer deposition (ALD),physical vapor deposition (PVD), such as thermal evaporation orsputtering. In some implementations, the protective film 160 isdeposited on the negative electrode structure 140 above the meltingpoint of lithium to facilitate chemical bonding. The protective film 160can be formed on the negative electrode structure 140 by a laminationprocess. The protective film 160 can be deposited below the meltingpoint of lithium and then the negative electrode structure 140heat-treated up to or above the melting point of lithium.

The protective film includes a thermoplastic film, such as apolyethylene, a polypropylene, a poly(ethylene terephthalate), apoly(butylene terephthalate), a polyester, a polyamide, a polyaramid, apolyacrylate, a polycarbonate, a poly(ester carbonate), apolybenzimidazole, a polyimide, a polyether imide, a polyamide imide,and the like.

The protective film 160 can be a conformal coating or a discrete film,either having a thickness in the range of 1 nanometer to 2,000nanometers (e.g., in the range of 10 nanometers to 600 nanometers; inthe range of 50 nanometers to 100 nanometers; in the range of 50nanometers to 200 nanometers; in the range of 100 nanometers to 150nanometers). In one example, the protective film 160 is a discrete filmhaving a thickness in the range of 1 micron to 50 microns (e.g., in therange of 1 micron to 25 microns). Coating process parameters control theprotective surface properties of the protective film 160 including, forexample, mechanical durability, hydrophobicity, and stickiness.Properties of the protective film 160 can be optimized to minimizereaction with air for extending coated web usable shelf life, tofacilitate battery substrate and device manufacturability including webhandling, and to contribute to stable SEI formation during batteryassembly and charging.

FIG. 2 illustrates a cross-sectional view of a molten metal coatingsystem 200 according to one or more implementations described herein.The molten metal coating system 200 includes a molten metal coatingmodule 230 according to one or more implementations described herein.The molten metal coating system 200 further includes an unwinding module220 operable to supply a flexible substrate such as a continuousflexible substrate 222 to the molten metal coating module 230. In oneexample, the continuous flexible substrate 222 prior to processingincludes negative current collector 150 and molten metal is formeddirectly on the current collector using the molten metal coating system200. In another example, the continuous flexible substrate 222 prior toprocessing includes negative current collector 150 and negativeelectrode structure 140 formed thereon and molten metal is formeddirectly on the negative electrode structure 140 using the molten metalcoating system 200. The molten metal coating module 230 further includesa winding module 240 operable to collect the flexible substrate from themolten metal coating module 230. The molten metal coating system 200 canbe operable for either single-sided or double-sided processing of aflexible substrate. In some implementations, the molten metal coatingsystem 200 is operable for depositing molten metal (e.g., moltenlithium) on flexible substrates followed by forming a passivation filmor a laminate film on the as deposited molten metal.

The molten metal coating system 200 can include any suitable structure,configuration, arrangement, and/or components that enable the moltenmetal coating system 200 to deposit molten metal and/or passivate thedeposited molten metal on the continuous flexible substrate 222according to implementations of the present disclosure. For example, insome implementations the molten metal coating system 200 includes, butis not limited to, suitable deposition systems including kiss-coaterrollers, Meyer bars, gravure rollers, air bearings, power sources,individual pressure controls, deposition control systems, load cells,servomotors, and temperature control components.

In some implementations, the molten metal coating system 200 includes achamber body 202. The chamber body 202 can be fabricated from standardmaterials, such as aluminum, quartz, ceramic, or stainless steel. Thechamber body 202 can be cooled by a fluid such as, for example, waterand/or a glycol-based fluid. The chamber body 202 defines an interiorvolume 203. Partition plates 204 a, 204 b (collectively 204) extendacross the interior volume 203 defined by the chamber body 202. Thepartition plate 204 a separates the interior volume 203 into anunwinding volume 206 operable to supply the continuous flexiblesubstrate 222 and a processing volume 207 in which molten metal isdeposited on the continuous flexible substrate 222. The partition plate204 b separates the interior volume 203 into the processing volume 207and a winding volume 208 operable to collect the processed continuousflexible substrate 222. The partition plates 204 a, 204 b include one ormore slits 209 a, 209 b (collectively 209) respectively foraccommodating the continuous flexible substrate 222. Each slit 209 inthe partition plate 204 is sized to accommodate the continuous flexiblesubstrate 222 while enabling differential pumping between the unwindingvolume 206, the processing volume 207, and/or the winding volume 208.

In some implementations, an inert gas environment is maintained in atleast one of the unwinding volume 206, the processing volume 207, and/orthe winding volume 208. The inert gas environment can include an inertgas selected from argon, nitrogen, or combinations of argon andnitrogen. The inert gas environment of the unwinding volume 206, theprocessing volume 207, and/or the winding volume 208 isolates (e.g.,provides gas separation) from the substantially ambient (e.g.,atmospheric) environment outside of the molten metal coating system 200,which reduces the likelihood of contamination of the as depositedlithium film. This inert gas environment of the unwinding volume 206,the processing volume 207, and/or the winding volume 208 also isolates(e.g., provides gas separation) the unwinding volume 206 from theprocessing volume 207 and the processing volume 207 from the windingvolume 208, if targeted. This isolation enables use of incompatiblechemistries in the unwinding volume 206, the processing volume 207,and/or the winding volume 208. In one example, the processing volume 207contains an argon gas environment and the winding volume 208 contains acombination of argon and a passivation gas (e.g., nitrogen).

In some implementations, at least one of the unwinding volume 206, theprocessing volume 207, and the winding volume 208 is coupled to apressure control system (not shown), which pumps down and vents theunwinding volume 206, the processing volume 207, and/or the windingvolume 208 as needed to facilitate passing the continuous flexiblesubstrate 222 between the inert gas environment and the substantiallyambient (e.g., atmospheric) environment outside of the molten metalcoating system 200.

The chamber body 202 includes one or more openings 210 a, 210 b, 210 c(collectively 210) for providing access to the interior volume 203. Inone example, as depicted in FIG. 2 , the one or more openings 210 arepositioned at a top of the chamber body 202. The one or more openings210 can be positioned at other locations of the chamber body 202, whichprovide access to the chamber components. The chamber body 202 canoptionally include a lid 212 a, 212 b, 212 c (collectively 212) that canopen and close to allow the user access to components within theinterior volume 203 of the chamber body 202. In one example, the chamberbody 202 includes transparent portions or windows used to monitorprocessing conditions within the chamber.

It should be understood that although the unwinding volume 206, theprocessing volume 207, and the winding volume 208 are shown as sharing acommon chamber body 202, in some implementations, the unwinding volume206, the processing volume 207, and the winding volume 208 are definedby separate chamber bodies with the chamber body defining the unwindingvolume 206 stacked upon or adjacent to (e.g., side-by-side) the chamberbody defining the processing volume 207, and/or the winding volume 208.For example, in some implementations, the molten metal coating system200 includes an unwinding chamber, which defines the unwinding volume206, a deposition chamber, which defines the processing volume 207, anda separate winding chamber, which defines the winding volume 208. Theunwinding chamber, the deposition chamber, and the winding chamber areseparate modular and stackable elements. In one example, the unwindingchamber is positioned adjacent to the deposition chamber and the windingchamber is positioned adjacent to the deposition chamber.

The molten metal coating system 200 is constituted as a roll-to-rollsystem including the unwinding module 220 operable to supply thecontinuous flexible substrate 222, the molten metal coating module 230operable to deposit molten metal on the continuous flexible substrate222, and the winding module 240 operable to form a passivation filmand/or laminate film on the molten metal in the winding module 240. Theunwinding module 220 includes an unwinding roller 250 operable to supplythe continuous flexible substrate 222. The winding module 240 includes awinding roller 260 operable to accept the processed continuous flexiblesubstrate 222. The molten metal coating system 200 can further include alaminate film supply roller 270 operable to supply a protective film 272to the processed continuous flexible substrate 222.

The continuous flexible substrate 222 is provided as a web, which iswound up on a roll, such as the unwinding roller 250. In one example,the continuous flexible substrate 222 has a width in a range from 15 cmto 300 cm, and typically has a width of approximately 160 cm. In anotherexample, the continuous flexible substrate 222 has a width in a rangefrom 5 cm to 200 cm, and typically has a width of approximately 10 cm.The continuous flexible substrate 222 has a thickness in a range from 8μm to 200 μm, for example, a thickness of approximately 50 μm. Thecontinuous flexible substrate 222 has a front surface 224 and a backsurface 226. In some implementations, after processing, the continuousflexible substrate 222 includes a flexible material having a lithiumelectrode structure and a passivation film formed thereon. For example,after processing, the continuous flexible substrate 222 can be thenegative current collector 150 having the negative electrode structure140 and protective film 160 formed thereon as shown in FIG. 1B. In oneexample, only the front surface 224 of the flexible substrate has alithium film and a protective film formed thereon. In another example,both the front surface 224 and the back surface 226 have metal films andpassivation films formed thereon.

In other implementations, after processing, the continuous flexiblesubstrate 222 includes a flexible material having a negative electrodestructure formed thereon, a lithium metal film formed on the negativeelectrode structure, and a passivation film formed thereon. For example,after processing, the continuous flexible substrate 222 includes thenegative current collector 150 having the negative electrode structure140, a metal film (e.g., lithium metal) formed on the negative electrodestructure, and protective film 160 formed on the metal film. In oneexample, only the front surface 224 of the flexible substrate has thenegative electrode structure 140, the metal film, and a protective film160 formed on the metal film. In another example, both the front surface224 and the back surface 226 have negative electrodes, metal films andpassivation films formed thereon.

In some implementations, the molten metal coating system 200 furtherincludes one or more molten metal coating modules 230 operable todeposit a molten metal film on the continuous flexible substrate 222optionally followed by formation of a protective film on the asdeposited molten metal film. In one example, the one or more moltenmetal coating modules 230 are operable to perform free-span processingof the continuous flexible substrate 222. In one implementation, themolten metal coating system 200 is operable to simultaneously orquasi-simultaneously process opposing sides of the continuous flexiblesubstrate 222. For example, a first molten metal application assemblyfaces the front surface 224 of the continuous flexible substrate 222 anda second molten metal application assembly faces the back surface 226 ofthe continuous flexible substrate 222. In another implementation, themolten metal coating system 200 is designed to sequentially processopposing sides of the continuous flexible substrate 222. For example, afirst molten metal application assembly faces the front surface 224 ofthe continuous flexible substrate 222 and a second molten metalapplication assembly is positioned downstream from the first moltenmetal application assembly and faces the back surface 226 of thecontinuous flexible substrate 222.

In some implementations, the molten metal coating system 200 includes acommon transport architecture 280. The common transport architecture 280can include any transfer mechanism capable of moving the continuousflexible substrate 222 through the unwinding volume 206, the processingvolume 207, and the winding volume 208. In some implementations, thecommon transport architecture 280 is a reel-to-reel system including theunwinding roller 250 and the winding roller 260. The unwinding roller250 and the winding roller 260 can be individually heated or cooleddepending upon the targeted process conditions. The unwinding roller 250and the winding roller 260 can be individually heated either using aninternal heat source positioned within each reel or an external heatsource. The unwinding roller 250 and the winding roller 260 can beindividually cooled using either an internal cooling source positionedwithin each reel or an external cooling source.

In some implementations, the common transport architecture 280 furtherincludes one or more auxiliary tension reels 282 a-282 g (collectively282) positioned between the unwinding roller 250 and the winding roller260. The auxiliary tension reels are disposed along the substrate traveldirection 228 where the continuous flexible substrate 222 is conveyedbetween the unwinding roller 250 and the winding roller 260, to allow atensile force to the continuous flexible substrate 222. This tensileforce prevents the continuous flexible substrate 222 from sagging downas well as to change the movement direction of the continuous flexiblesubstrate 222. Accordingly, even though the continuous flexiblesubstrate 222 is moved along a continuously long path, a certainmovement rate is constantly maintained. In some implementations, any ofthe auxiliary tension reels 282 can be replaced with gas cushionrollers. The auxiliary tension reels 282 can be individually heatedeither using an internal heat source positioned within each reel or anexternal heat source. The auxiliary tension reels 282 can beindividually cooled using either an internal cooling source positionedwithin each reel or an external cooling source.

In some implementations, the common transport architecture 280 furtherincludes one or more servomotors 284 a-284 f (collectively 284) foradvancing the continuous flexible substrate 222. The one or moreservomotors 284 allow for precise control of linear position, velocity,and/or acceleration of the continuous flexible substrate 222. The one ormore servomotors can be coupled with a sensor for position feedback.

In some implementations, the common transport architecture 280 furtherincludes one or more load cells 286 a-286 b (collectively 286) forconverting web tension into an electrical signal that can be measuredand standardized.

In some implementations, the molten metal coating system 200 furtherincludes the laminate film supply roller 270 operable to supply theprotective film 272 to the processed continuous flexible substrate 222.The protective film 272 provides protection to the processed continuousflexible substrate 222. The protective film 272 is removed prior tocombining the processed continuous flexible substrate 222 with a cathodestructure to form an energy storage device (e.g., a lithium-ion storagedevice or capacitor). In one example, the protective film 272 includes athermoplastic film, such as a polyethylene, a polypropylene, apoly(ethylene terephthalate), a poly(butylene terephthalate), apolyester, a polyamide, a polyaramid, a polyacrylate, a polycarbonate, apoly(ester carbonate), a polybenzimidazole, a polyimide, a polyetherimide, a polyamide imide, and the like. The laminate film supply roller270 is positioned in the winding volume 208 to supply the protectivefilm 272 to the front surface 224 of the continuous flexible substrate222 after processing and prior to winding the continuous flexiblesubstrate 222 on the winding roller 260.

Generally, the molten metal coating system 200 includes a systemcontroller 290 operable to control the automated aspects of the moltenmetal coating system 200. The system controller 290 can be provided andcoupled to various components of the molten metal coating system 200 tocontrol the operation thereof. The system controller 290 includes acentral processing unit (CPU) 292, a memory 294, and support circuits296. The system controller 290 can control the molten metal coatingsystem 200 directly, or via computers (or controllers) associated withparticular process chamber and/or support system components. The systemcontroller 290 can be one of any form of general-purpose computerprocessor that can be used in an industrial setting for controllingvarious chambers and sub-processors. The memory, or computer readablemedium, 294 of the system controller 290 can be one or more of readilyavailable memory such as random access memory (RAM), read only memory(ROM), floppy disk, hard disk, optical storage media (e.g., compact discor digital video disc), flash drive, or any other form of digitalstorage, local or remote. The support circuits 296 are coupled to theCPU 292 for supporting the processor in a conventional manner. Thesecircuits include cache, power supplies, clock circuits, input/outputcircuitry and subsystems, and the like. The methods as described hereincan be stored in the memory 294 as software routine that can be executedor invoked to control the operation of the molten metal coating system200 in the manner described herein. The software routine can also bestored and/or executed by a second CPU (not shown) that is remotelylocated from the hardware being controlled by the CPU 292. In oneexample, the system controller 290 is operable to control the travelrate of the continuous flexible substrate 222 by monitoring load cells286 and controlling the servomotors 284.

In one implementation, the molten metal coating system 200 is positionedin a secondary containment unit 298. In one implementation, thesecondary containment unit 298 is a glove box, which is filled with aninert gas, such as argon.

In operation, the continuous flexible substrate 222 is conveyed from theunwinding roller 250 advancing into the molten metal coating module 230.The continuous flexible substrate 222 travels from the unwinding volume206 through slit 209 a, advancing into the processing volume 207 of themolten metal coating module 230. In the processing volume 207, thecontinuous flexible substrate 222 is exposed to a coating process todeposit a molten metal film on the continuous flexible substrate 222.The continuous flexible substrate 222 travels through slit 209 b,advancing from the processing volume 207 into the winding volume 208. Inthe winding volume 208, the protective film 272 is supplied onto themolten metal film on the front surface 224 of the processed continuousflexible substrate 222 prior to winding the processed continuousflexible substrate 222 on the winding roller 260.

FIG. 3A illustrates a schematic cross-sectional view of one example of akiss coating module 300 according to one or more implementationsdescribed herein. The kiss coating module 300 can be used in place ofthe molten metal coating module 230 depicted in FIG. 2 . The kisscoating module 300 includes a pick-up roll or kiss roller 310. The kissroller 310 is a cylinder (e.g., a steel cylinder) having a surface 314.The surface 314 can be smooth surface. The surface 314 picks up bycontact a wet film comprising molten metal 312, such as molten lithium,from a primary melt pool 320 and delivers it to the front surface 224 ofthe moving continuous flexible substrate 222. The kiss roller 310 canfurther include a servomotor 284 g.

In one implementation, the kiss roller 310 contacts the continuousflexible substrate 222 while traveling in an anti-direction meaning thatthe kiss roller rotates in a direction that is opposite the traveldirection of the continuous flexible substrate 222 (i.e., contact inanti-direction). In another implementation, the kiss roller 310 does notcontact the continuous flexible substrate 222 while rotating in the samedirection as the travel direction of the continuous flexible substrate222 (i.e., contact-free in co-direction). In yet another implementation,the kiss roller 310 contacts the continuous flexible substrate 222 whilerotating in the same direction as the travel direction of the continuousflexible substrate 222 (i.e., contact in co-direction).

The kiss coating module 300 further includes a Meyer rod 324, which ispositioned downstream from the kiss roller 310. After the wet film isapplied to the front surface 224 of the continuous flexible substrate222, the continuous flexible substrate 222 is then drawn across theMeyer rod 324. The Meyer rod 324, which functions as a metering device,is operable to control the gap and shape of the downstream molten metalmeniscus formed on the continuous flexible substrate 222. Meteringallows for production of repeatable and uniformly thick coating ofmolten metal coatings. In one example, the Meyer rod 324 is a ¼ inch to½ inch diameter stainless steel drill rod stock individually spirallywrapped with various gauges of stainless steel wire. Between each wrap(turn of wire) is a “V” groove shape: as wire gauge increases, the sizeof the groove becomes larger, thus allowing a thicker layer of the wetfilm to be defined on the front surface 224 of the continuous flexiblesubstrate 222. The Meyer rod 324, for example, ensures that a fairlyuniform wet film of approximately 10 to 20 microns can be wet cast ontothe continuous flexible substrate 222.

The kiss coating module 300 can further include auxiliary tension reels282 e-282 g. In addition, the kiss coating module 300 can furtherinclude additional kiss rollers, Meyer bars, gravure rollers, airbearings, power sources, individual pressure controls, depositioncontrol systems, load cells, servomotors, and temperature controlcomponents.

The kiss coating module 300 further includes the primary melt pool 320operable to supply molten metal to the kiss roller 310 enabling thetransfer of molten metal onto the continuous flexible substrate 222. Thekiss coating module 300 further includes a secondary melt pool 340operable to supply the primary melt pool 320 with molten metal at atargeted temperature. The primary melt pool 320 and the secondary meltpool 340 can be decoupled from each other. In some implementations,where the primary melt pool 320 and the secondary melt pool 340 aredecoupled from each other, the secondary melt pool 340 is operable formelting metal ingots to form the molten metal.

In one implementation, the secondary melt pool 340 is coupled with anengagement mechanism 350. The engagement mechanism 350 is operable tomove the secondary melt pool 340 radially toward the primary melt pool320. In one example, the engagement mechanism 350 is a pneumaticcylinder. Other suitable engagement mechanisms capable of moving thesecondary melt pool 340 radially toward and radially away from theprimary melt pool 320 can be used. For example, hydraulic cylinders,pneumatic cylinders, and motorized sliders are alternatives.

In one implementation, the kiss roller 310 includes one or more internalheater(s) 352, for example, a coaxial cartridge heater. The internalheater 352 is operable to keep the wetted surfaces above the meltingtemperature of the molten metal to prevent premature solidification.Other heating methods and apparatus such as, for example, heater fluidbars and rollers, embedded electric resistance heaters, infrared heatinglamps, and contact heaters, can be used. Electrical power can be fed tothe internal heater(s) 352 through one or more slip ring assemblies.However, the thermal operating limit of the slip ring assemblies, whichis typically lower than the target set point temperature of the roller.In one implementation, the rotating slip ring assemblies are isolatedfrom the kiss roller 310 with a poor thermal conductor adaptor, forexample, an adapter made from PEEK or other similar materials.

In one implementation, the kiss roller 310 and/or the Meyer bar ispre-loaded, for example, spring loaded. Pre-loading of the kiss roller310 and/or Meyer bar ensures continuous contact of the kiss roller 310with the continuous flexible substrate 222. In one implementation,constant force hydraulic cylinders, constant force pneumatic cylinders,or motorized sliders are used to move the kiss roller 310 and/or theMeyer bar. Pre-loading of the kiss roller 310 and/or the Meyer baragainst the continuous flexible substrate 222 helps compensate forthermal expansion of the gap defining components during thermal rampingand changes.

The primary melt pool 320 is operable to supply sufficient molten metalto the kiss roller 310 enabling the transfer of molten metal to thecontinuous flexible substrate 222. In one implementation, the primarymelt pool 320 is positioned on a heater 354 operable to maintain themolten metal 312 in a molten state. The primary melt pool 320 caninclude one or more internal heaters operable to keep the moltenmaterial in a molten state. The one or more internal heaters can be, forexample, coaxial cartridge heaters.

The secondary melt pool 340 is operable to supply sufficient moltenmetal to the primary melt pool 320 at a targeted temperature. In oneimplementation, the secondary melt pool 340 includes one or moreinternal heaters 344 a-d (collectively 344) operable to melt the metalingots and keep the molten material in a molten state. The one or moreinternal heaters 344 can be, for example, coaxial cartridge heaters. Thesecondary melt pool 340 can be a hinged pool with an actuator thatcontrols the tilt of the secondary melt pool 340 causing the moltenmetal to flow over a ledge into the primary melt pool 320. The primarymelt pool 320 can be coupled with a load cell, which provides a loadcell signal of a direct weight measurement of the primary melt pool 320.The load cell signal is fed back to the system controller 290. In oneimplementation, sensors (e.g., optical, capacitive, ultrasonic or thelike) detect a lower and upper level range of the molten metalrespectively and provide the signals to the system controller 290 forthe actuator motion. The actuator can be a pneumatic cylinder plumbed toa proportional control valve.

In another implementation, the primary melt pool 320 is replenished withhigh purity material in the form of a wire or foil. The wire or foil ispreheated to below the melt temperature to minimize thermal loss in theprimary melt pool 320 and acts as a thermal sink. A drive mechanismcontrols the feed rate of the wire or foil resulting in a known flowrate based on a known cross section. The flow rate matches the productof deposition cross section and web speed.

FIG. 3B illustrates a schematic cross-sectional view of one example of akiss roller 310 that can be used with the coating module of FIG. 3Aaccording to one or more implementations of the present disclosure. Inone implementation, the surface 314 of the kiss roller 310 is a convexsurface or a “crowned” surface. Not to be bound by theory but it isbelieved that crowning the surface of the kiss roller to make a length316 of the convex portion of the surface 314 substantially equal to alength 318 of the heated section of the foil minimizes wrinkles andhomogenizes pressure in the contact zone. In the cold state, thecontinuous flexible substrate 222 contacts the surface 314 of the kissroller 310 in the center, whereas in the heated state, the continuousflexible substrate 222 contacts entire surface 314 of the kiss roller310.

FIG. 4 illustrates a schematic cross-sectional view of a slot-diecoating module 400 according to one or more implementations describedherein. The slot-die coating module 400 can be used in place of themolten metal coating module 230 depicted in FIG. 2 . The slot-diecoating module 400 includes one or more slot-die 410 a, 410 b(collectively 410) operable to deposit a wet film comprising moltenmetal on the continuous flexible substrate. In one implementation, theone or more slot-die 410 a, 410 b are arranged to process opposing sidesof the continuous flexible substrate 222. For example, as depicted inFIG. 4 , a first slot-die 410 a faces the front surface 224 of thecontinuous flexible substrate 222 and a second slot-die 410 b faces theback surface 226 of the continuous flexible substrate 222.

In one implementation, the one or more slot-die 410 are positioned inthe processing volume 207 such that the slot-die delivers the materialto be deposited at an angle relative to a substrate travel direction 228of the continuous flexible substrate 222. The one or more slot-die 410can be positioned such that a material to be deposited on the continuousflexible substrate 222 is delivered in a substantially perpendicularorientation relative to the substrate travel direction 228 of thecontinuous flexible substrate 222. The one or more slot-die 410 can bepositioned such that a material to be deposited on the continuousflexible substrate 222 is delivered simultaneously on opposing sides ofthe continuous flexible substrate 222 in free span in a substantiallyperpendicular orientation relative to the substrate travel direction 228of the continuous flexible substrate 222. In one implementation, amaterial to be deposited is delivered in an outflow direction having anangle between about 0 and 60 degrees relative to the horizon, forexample, between about 1 degree and about 45 degrees, such as betweenabout 5 degrees and about 15 degrees. In another implementation, amaterial to be deposited is delivered in an outflow direction having anangle between about 180 and 240 degrees relative to the horizon, forexample, between about 181 degree and about 225 degrees, such as betweenabout 185 degrees and about 195 degrees.

In one implementation, the slot-die 410 includes one or more heaters 414a-414 d (collectively 414) operable to control the temperature of themolten metal within the slot-die 410. The slot-die operating temperatureis typically set to maximize wetting control, which is dependent on themolten metal flowing through the slot-die. The slot-die 410 can beoperated in bead mode where a gap is present between the lips of theslot die and the surface of the continuous flexible substrate 222. Theslot-die can be operated in impregnation mode where the lips of theslot-die contact the continuous flexible substrate 222.

The common transport architecture 280 of the slot-die coating module 400can further include auxiliary tension reels 282 h-282 i. The commontransport architecture 280 of the slot-die coating module 400 canfurther include process rollers 412 a, 412 b (collectively 412) overwhich the continuous flexible substrate 222 travels during depositionfrom each corresponding slot-die 410. The process rollers 412 can beheated in order to reduce the number of wrinkles that form in thecontinuous flexible substrate 222 as the continuous flexible substrate222 travels over the process rollers 412. In implementations where theprocess roller is heated, the process roller includes one or moreinternal heater(s) 413 a, 413 b (collectively 413), for example, acoaxial cartridge heater. The common transport architecture 280 of theslot-die coating module 400 can further include load cells 286 c, 286 d.The common transport architecture 280 of the slot-die coating module 400can further include a servomotor 284 h. In addition, the slot-diecoating module 400 can further include additional slot-die, Meyer bars,gravure rollers, air bearings, power sources, individual pressurecontrols, deposition control systems, additional load cells, additionalservomotors, and temperature control components.

The slot-die coating module 400 further includes a molten metalreplenishment system. Similar to the kiss coating module 300, theslot-die coating module 400 includes a primary melt pool 320 and asecondary melt pool 340. The primary melt pool 320 supplies molten metalto each of the slot-die 410 a, 410 b. The primary melt pool 320 isfluidly coupled with each of the slot-die 410 a, 410 b via a fluidsupply line 420.

The molten metal replenishment system further includes a pump 488operable to move the liquid lithium from the primary melt pool 320 tothe slot-die 410. The molten metal replenishment system optionallyincludes a flow meter 490 operable to monitor the flow of liquid lithiumthrough the supply line 420. In at least one aspect, the flow meter 490is positioned downstream from the pump 488. The pump 488 can be anysuitable pump operable to move the molten metal. In at least one aspect,the pump 488 is an electromagnetic pump that moves molten metal usingelectromagnetism. The electromagnetic pump can be an electromagneticpump of any type. In at least one aspect, the electromagnetic pumpcauses an electromagnetic force to act on the molten metal by an inducedcurrent flowing through the liquid lithium due to a moving magneticfield generated by a direct or alternating current and the movingmagnetic field, thus discharging the liquid lithium in the samedirection as a moving direction of the magnetic field. The flow meter490 can be any suitable flow meter for measuring the flow of the liquidlithium. The flow meter 490 can communicate with the pump 488 and/or ashut-off valve via a feedback loop (not shown).

FIG. 5 illustrates a schematic cross-sectional view of one example of agravure coating module 500 according to one or more implementationsdescribed herein. The gravure coating module 500 can be used in place ofthe molten metal coating module 230 depicted in FIG. 2 . The gravurecoating module 500 includes a gravure roller 510, a backup roller 520,and a doctor blade 530. The gravure roller 510 is a cylinder (e.g., asteel cylinder) that picks up by contact a wet film comprising of moltenmetal 312, such as molten lithium from the primary melt pool 320 anddelivers it to the front surface 224 of the moving continuous flexiblesubstrate 222. The gravure roller 510 has a surface 512 that includes atleast one of stainless steel, copper, chromium, or a combinationthereof. In one example, the surface of the gravure roller 510 isstainless steel. The surface of the gravure roller 510 has patterned orengraved portions. Examples of engraved surfaces of the gravure roller510 include separate cavities, connected cavities formed by sinusoidallines leaving a channel open for exchange, and/or helical grooves. Thegravure roller 510 can be heated by an internal heater, such as theinternal heater 552.

The gravure roller 510 can further include a servomotor 284 i. The levelof molten metal 312 in the primary melt pool 320 is such that wettingcontact with the gravure roller 510 is maintained. The doctor blade 530removes excess molten metal from the gravure roller so that only theengraved portions of the surface 512 of the gravure roller 510 holdmolten metal 312. The backup roller 520 presses the continuous flexiblesubstrate 222 against the gravure roller 510 to form nip 540. The backuproller 520 can further include a servomotor 284 j. Within the nip 540, aportion of the molten metal is transferred to the continuous flexiblesubstrate 222. In one implementation, the doctor blade 530 is replacedwith a copper sponge. The backup roller 520 is a cylinder (e.g., asilicone cylinder).

In one implementation, the gravure roller 510 contacts the continuousflexible substrate 222 while traveling in an anti-direction meaning thatthe gravure roller 510 rotates in a direction that is opposite thetravel direction of the continuous flexible substrate 222 (i.e., contactin anti-direction). In another implementation, the gravure roller 510does not contact the continuous flexible substrate 222 while rotating inthe same direction as the travel direction of the continuous flexiblesubstrate 222 (i.e., contact-free in co-direction). In yet anotherimplementation, the gravure roller 510 contacts the continuous flexiblesubstrate 222 while rotating in the same direction as the traveldirection of the continuous flexible substrate 222 (i.e., contact inco-direction).

In one implementation, the gravure coating module 500 further includes abrush 560 operable to remove any film or skin material, for example,lithium films that can form in the cavities of the gravure roller 510.As depicted in FIG. 5 , the brush 560 is positioned to remove materialfrom the cavities in a portion of the gravure roller 510 prior to theportion of the gravure roller 510 contacting the molten metal 312 in theprimary melt pool 320. The brush 560 removes contaminants and particlesfrom the cavities of the gravure roller 510, which helps maintain thevolume of the cavities formed in the surface of the gravure roller 510.The brush 560 is rotatable. The brush 560 can be actively heated.

In addition, the gravure coating module 500 can further includeauxiliary tension rolls, process rollers, Meyer bars, air bearings,power sources, individual pressure controls, deposition control systems,load cells, servomotors, and temperature control components.

The gravure coating module 500 further includes a molten metalreplenishment system. Similar to the kiss coating module 300, thegravure coating module 500 includes the primary melt pool 320 and asecond melt pool 340 for replenishing the molten metal 312 in theprimary melt pool 320.

FIG. 6 illustrates a process flow chart summarizing one implementationof a processing sequence 600 of forming a lithium electrode structureaccording to one or more implementations of the present disclosure. Theprocessing sequence 600 can be used to form a single-sided lithiumelectrode structure, for example, the lithium electrode structuredepicted in FIG. 1A, or a dual-sided electrode structure, for example,the electrode structure depicted in FIG. 1B. The processing sequence 600can be performed using, for example, the molten metal coating system 200depicted in FIG. 2 .

The processing sequence 600 begins at operation 610 by providing aflexible substrate. In one implementation, the flexible substrate is thecontinuous flexible substrate 222, which includes the negative currentcollector 150. In another implementation, the flexible substrate is thecontinuous flexible substrate 222, which includes the negative currentcollector 150 having the negative electrode structure 140 formedthereon. The flexible substrate is supplied by the unwinding roller 250positioned in the unwinding module 220.

At operation 620, the flexible substrate is moved into the processingvolume 207. Referring to FIG. 2 , the continuous flexible substrate 222is conveyed from the unwinding roller 250 into the processing volume207. In some implementations, the processing volume 207 contains aninert gas environment such as an argon gas environment.

At operation 630, the continuous flexible substrate 222 is exposed to amolten metal (e.g., molten lithium) to deposit a thin layer of moltenlithium on the continuous flexible substrate. The flexible substrate ismoved through the molten metal coating module 230 where a thin layer ofmolten lithium is formed on the continuous flexible substrate 222 by themolten metal coating module 230.

In one implementation, the thin layer of molten lithium is deposited onthe continuous flexible substrate 222 via a kiss coating process using akiss coating module, such as the kiss coating module 300 depicted inFIG. 3 . With reference to FIG. 3 , molten lithium is applied to thecontinuous flexible substrate 222 by the kiss roller 310. Duringapplication of the molten lithium to the continuous flexible substrate222, the kiss roller 310 is maintained a temperature such that thelithium remains in a molten state. The kiss roller 310 can be heated byan internal heater, such as the internal heater 352. The molten lithiumcoating is post metered by a wire wound rod, such as the Meyer rod 324that remove excess molten lithium coating from the continuous flexiblesubstrate 222. Typically, an excess of the molten lithium coating isdeposited onto the continuous flexible substrate 222 as it passes thekiss roller 310. The Meyer rod 324 allows the targeted quantity of themolten metal coating to remain on the continuous flexible substrate 222.The quantity of molten metal coating is determined by the diameter ofthe wire used on the Meyer rod 324.

In another implementation, the thin layer of molten lithium is depositedon the continuous flexible substrate 222 via a slot-die process using aslot-die coating module, such as the slot-die coating module 400depicted in FIG. 4 . With reference to FIG. 4 , a molten lithium coatingis applied to the continuous flexible substrate 222 by the slot-die 410.The molten lithium coating can be applied to the front surface 224 ofthe continuous flexible substrate 222 via slot-die 410 a and to the backsurface 226 by the second slot-die 410 b. During application of themolten lithium to the continuous flexible substrate 222, the slot-die ismaintained at a temperature such that the lithium remains in a moltenstate.

In yet another implementation, the thin layer of molten lithium isdeposited on the continuous flexible substrate 222 via a gravure coatingprocess using a gravure coating module, such as the gravure coatingmodule 500 depicted in FIG. 5 . With reference to FIG. 5 , moltenlithium is applied to the continuous flexible substrate 222 by thegravure roller 510. The gravure roller 510 picks up by contact a wetfilm comprising molten lithium, such as molten lithium from the primarymelt pool 320 and delivers it to the front surface 224 of the movingcontinuous flexible substrate 222. The doctor blade 530 removes excessmolten lithium so that only the engraved portions of the circumferentialsurface of the gravure roller 510 hold molten metal 312. The backuproller 520 presses the continuous flexible substrate 222 against thegravure roller 510 to form nip 540. Within the nip 540, a portion of themolten metal is transferred to the continuous flexible substrate 222.During application of the molten lithium to the continuous flexiblesubstrate 222, the gravure roller 510 is maintained a temperature suchthat the lithium remains in a molten state.

During operation 630, the level of molten metal 312 in the primary meltpool 320 is such that wetting contact with either the kiss roller 310 orthe gravure roller 510 is maintained. In one implementation, thesecondary melt pool 340 is used to melt metal ingots and maintain anample supply of molten lithium to compensate for refilling the depletedmolten lithium from the primary melt pool 320. In anotherimplementation, the metal ingots are melted in the primary melt pool320. Once sufficient molten lithium is available in the primary meltpool 320, the kiss roller 310, the slot-die 410, or the gravure roller510 is exposed to a wetting process. Additional heat can be applied tothe kiss roller 310, the slot-die 410, or the gravure roller 510 duringthe wetting process. Upon contact, molten lithium is transferred ontothe continuous flexible substrate 222 coating the continuous flexiblesubstrate 222 in a defined manner (width and thickness). The processcontinues until a targeted coating length is produced. After operation630, the molten lithium can be solidified and melted again for the nextrun.

In one implementation, the processed continuous flexible substrate isexposed to a cooling process. The cooling process can be accomplished bypassing the continuous flexible substrate 222 between two fluid cooledplates coupled via an appropriate coupling gas such as argon or helium.The cooling process can be accomplished using cooling plates, coolingdrums, and/or cooling rollers.

At operation 640, the processed flexible substrate is moved into thewinding volume 208. Referring to FIG. 2 , in some implementations, thecontinuous flexible substrate 222 having the layer of lithium formedthereon is conveyed from the molten metal coating module 230 and passesthrough the slit 209 b into the winding volume 208. In oneimplementation, the winding volume 208 contains an inert gas, apassivation gas, or combination of inert gas and passivation gas, suchas an argon gas and nitrogen gas environment.

Optionally, at operation 650 the processed flexible substrate iscombined with a laminate film. The laminate film prevents the rewoundcoated flexible substrate from sticking to itself. Referring to FIG. 2 ,the processed continuous flexible substrate 222 is combined with theprotective film 272, which protects the processed front surface 224 ofthe processed continuous flexible substrate 222. The continuous flexiblesubstrate 222 is then wound on the winding roller 260.

The continuous flexible substrate 222 can be subjected to additionalprocessing. Additional processing can provide for deposition of aseparator, an electrolyte soluble binder, or in some implementations,additional chambers can provide for formation of a positive electrodestructure. In some implementations, additional chambers provide forcutting of the negative electrode. The laminate film can be removedafter cutting of the negative electrode.

In summary, some of the benefits of the present disclosure include theefficient integration of molten metal deposition and lamination into amodular processing system. In addition, it has been found by theinventors that some implementations of the present disclosure reducewrinkles and pattern formation when depositing molten metal on asubstrate in a roll-to-roll process. A slight drop in temperature canalter the viscosity of the molten material to the point that thematerial transfer and the flow behavior of the molten material leads toinconsistent deposition thicknesses and non-uniformities. For thesereasons, in some implementations, the surface temperature of thedeposition applicators should remain above the melt temperature of themetal. There are multiple methods of heating and controlling a surfacetemperature of such applicators. In addition, methods and apparatus formaintaining the temperature of the molten metal baths prior todeposition are also provided.

When introducing elements of the present disclosure or exemplary aspectsor implementation(s) thereof, the articles “a,” “an,” “the” and “said”are intended to mean that there are one or more of the elements.

The terms “comprising,” “including” and “having” are intended to beinclusive and mean that there can be additional elements other than thelisted elements.

While the foregoing is directed to implementations of the presentdisclosure, other and further implementations of the disclosure can bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

The invention claimed is:
 1. A system, comprising: a chamber bodydefining an interior volume; a first partition plate extending acrossthe interior volume separating the interior volume into a processingvolume and an unwinding volume; a second partition plate extendingacross the interior volume separating the interior volume into theprocessing volume and a winding volume; a reel-to-reel system operableto transport a continuous flexible substrate, comprising: an unwindingroller positioned in the unwinding volume, on which the continuousflexible substrate is wound prior to processing, and operable to unwindand release the continuous flexible substrate for the processing; and awinding roller positioned in the winding volume and operable to receivethe continuous flexible substrate following the processing, and operableto wind the continuous flexible substrate thereon; and a molten metalcoating assembly positioned in the processing volume and comprising: agravure roller having a patterned surface that picks up by contact a wetfilm comprising molten metal and deposits the wet film on the continuousflexible substrate; a primary melt pool operable to supply the moltenmetal to the gravure roller; a secondary melt pool operable to replenishthe molten metal in the primary melt pool; and an engagement mechanismcoupled with the secondary melt pool and operable to move the secondarymelt pool radially toward and radially away from the primary melt pool.2. The system of claim 1, further comprising a doctor blade positionedto removes excess molten metal from the gravure roller so that onlypatterned portions of the patterned surface of the gravure roller holdmolten metal.
 3. The system of claim 1, wherein the gravure rollercomprises one or more internal heaters operable to control a temperatureof the molten metal within the gravure roller.
 4. The system of claim 1,further comprising one or more process rollers disposed along a travelpath over which the continuous flexible substrate is conveyed betweenthe unwinding roller, the gravure roller, and the winding roller.
 5. Thesystem of claim 4, wherein the process rollers are positioned so thatthe gravure roller deposits molten metal on the continuous flexiblesubstrate while the continuous flexible substrate travels over one ofthe process rollers.
 6. The system of claim 5, wherein the processrollers further comprises an internal heater.
 7. The system of claim 1,further comprising a laminate film supply roller positioned in thewinding volume and operable to supply a laminate film over the depositedmolten metal.
 8. The system of claim 1, further comprising one or moreauxiliary tension reels disposed along a travel path where thecontinuous flexible substrate is conveyed between the unwinding roller,the gravure roller, and the winding roller.
 9. The system of claim 1,wherein the engagement mechanism is a pneumatic cylinder.
 10. The systemof claim 1, where in the primary melt pool is positioned on a heateroperable to maintain the molten metal in a molten state.
 11. A system,comprising: a chamber body defining an interior volume; a firstpartition plate extending across the interior volume separating theinterior volume into a processing volume and an unwinding volume; asecond partition plate extending across the interior volume separatingthe interior volume into the processing volume and a winding volume; areel-to-reel system operable to transport a continuous flexiblesubstrate, comprising: an unwinding roller positioned in the unwindingvolume, on which the continuous flexible substrate is wound prior toprocessing, and operable to unwind and release the continuous flexiblesubstrate for the processing; and a winding roller positioned in thewinding volume and operable to receive the continuous flexible substratefollowing the processing, and operable to wind the continuous flexiblesubstrate thereon; and a molten metal coating assembly positioned in theprocessing volume and comprising: a gravure roller having a patternedsurface that picks up by contact a wet film comprising molten metal anddeposits the wet film on the continuous flexible substrate; a primarymelt pool operable to supply the molten metal to the gravure roller; asecondary melt pool operable to replenish the molten metal in theprimary melt pool; and an engagement mechanism is a pneumatic cylinderand coupled with the secondary melt pool and operable to move thesecondary melt pool radially toward and radially away from the primarymelt pool.
 12. The system of claim 11, further comprising a doctor bladepositioned to removes excess molten metal from the gravure roller sothat only patterned portions of the patterned surface of the gravureroller hold molten metal.
 13. The system of claim 11, wherein thegravure roller comprises one or more internal heaters operable tocontrol a temperature of the molten metal within the gravure roller. 14.The system of claim 11, further comprising one or more process rollersdisposed along a travel path over which the continuous flexiblesubstrate is conveyed between the unwinding roller, the gravure roller,and the winding roller.
 15. The system of claim 14, wherein the processrollers are positioned so that the gravure roller deposits molten metalon the continuous flexible substrate while the continuous flexiblesubstrate travels over one of the process rollers.
 16. The system ofclaim 15, wherein the process rollers further comprises an internalheater.
 17. The system of claim 11, further comprising a laminate filmsupply roller positioned in the winding volume and operable to supply alaminate film over the deposited molten metal.
 18. The system of claim11, further comprising one or more auxiliary tension reels disposedalong a travel path where the continuous flexible substrate is conveyedbetween the unwinding roller, the gravure roller, and the windingroller.
 19. The system of claim 11, wherein the engagement mechanism isoperable to move the secondary melt pool radially toward and radiallyaway from the primary melt pool.
 20. The system of claim 11, where inthe primary melt pool is positioned on a heater operable to maintain themolten metal in a molten state.